[DE] VERFAHREN ZUR HERSTELLUNG VON QUARTÄREN AMMONIUM-VERBINDUNGEN [EN] METHOD FOR PRODUCING QUATERNARY AMMONIUM COMPOUNDS [FR] PROCÉDÉ DE PRODUCTION DE COMPOSÉS D'AMMONIUM QUATERNAIRES
Crystal Structures of Two Complexes of the Rare-Earth-DOTA-Binding Antibody 2D12.5: Ligand Generality from a Chiral System
摘要:
We report the crystal structures of antibody 2D12.5 Fab bound to an yttrium-DOTA analogue and separately to a gadolinium-DOTA analogue. The rare earth elements have many useful properties as probes, and 2D12.5 binds the DOTA (1,4,7,10-tetraazacyclododecane-N,N",N",IV""-tetraacetic acid) complexes of all of them (Corneillie et al. J. Am. Chem. Soc. 2003, 125, 3436-3437). The structures show that there are no direct protein-metal interactions: a bridging water acts as a link between the protein and metal, with the chelate present as the M isomer in each case. DOTA forms an amphipathic cylinder with the charged carboxylate groups toward the face of the chelate near the metal ion, while nonpolar methylene groups from the macrocycle and the carboxymethyl groups occupy the rear and sides of the molecule. The orientation of the metal-DOTA in the 2D12.5 complex places most of the methylene carbon atoms of DOTA in hydrophobic contact with aromatic protein side chains. Other binding interactions between the metal complex and the antibody include a bidentate salt bridge, four direct H-bonds, and four to five water-mediated H-bonds. We find that 2D12.5 exhibits enantiomeric binding generality, binding yttrium chelates in both Delta(deltadeltadeltadelta) and Delta(lambdalambdalambdalambda) configurations with modestly different affinities. This develops from the symmetrical nature of the DOTA chelate, which places heteroatoms and hydrophobic atoms in approximately the same relative positions regardless of the helicity of DOTA.
Room-Temperature Copper-Catalyzed Carbon-Nitrogen Coupling of Aryl Iodides and Bromides Promoted by Organic Ionic Bases
作者:Chu-Ting Yang、Yao Fu、Yao-Bing Huang、Jun Yi、Qing-Xiang Guo、Lei Liu
DOI:10.1002/anie.200903158
日期:2009.9.21
solubility alone does not explain the performance of organic ionic bases in the room‐temperature coupling of aryl iodides and even bromides with aliphatic and aromatic amines and N‐heterocycles (NuH; see scheme). Conductivity measurements show that these organic ionic bases, which contain tetraalkylammonium or ‐phosphonium cations, are readily ionized in organic solvents.
Quaternaryammoniumsalts were synthesized from ammoniumsalts and dialkyl carbonates over imidazolium ionic liquid catalysts. The reaction gave almost stoichiometric amounts of the quaternaryammoniumsalts for halides and nitrates. It was found that the electron-donating property of the alkyl moieties of ammonium cations, the electrophilic nature of the alkyl group of the carbonate, the acidity of
Enantiopure A4L4 tetrahedral cages were obtained through chirality transfer in the anion-coordination-driven assembly (ACDA) of chiral C3-symmetric tris-bis(urea) ligands with phosphate.
Peripheral Templation-Modulated Interconversion between an A<sub>4</sub>
L<sub>6</sub>
Tetrahedral Anion Cage and A<sub>2</sub>
L<sub>3</sub>
Triple Helicate with Guest Capture/Release
An anion‐coordination‐based A4L6 (“A” denotes anion and “L” is ligand) tetrahedralcage was constructed by a C2‐symmetric bis‐bis(urea) ligand and phosphate anion, which showed reversible interconversion with the A2L3 triple helicate as a response to the template, concentration, or solvent. Notably, an unusual “peripheral” templation was found to be critical to stabilize the tetrahedral structure.
基于阴离子配位的A 4 L 6(“ A”表示阴离子,“ L”是配体)由C 2对称的双-双(脲)配体和磷酸根阴离子构成四面体笼,表明与阴离子具有可逆的相互转化。阿2大号3三重helicate为模板,浓度,或溶剂中的反应。值得注意的是,发现异常的“外围”模板对于稳定四面体结构至关重要。利用这种外围效应来组装一个“空的” A 4 L 6笼子,该笼子可以通过多种刺激控制地捕获/释放生物学上重要的物种,例如胆碱和乙酰胆碱。
Anion-Coordination-Driven Assembly of Chiral Quadruple and Single Helices Controlled by Countercations
Enantiopure helical assemblies were constructed by chiral C2-symmetric bis-bis(urea) ligands (LS/R) with phosphate or hydrogen phosphate anion, which is dictated by the countercation. In the presence of smaller cations (TMA+ or TEA+), the chiral ligands coordinate to dihydrated phosphate to form homochiral quadruple helicates (TMA)6[(PO4·2H2O)2LS/R4]. However, when larger cations (TPA+ or TBA+) were used, the ligand tends to assemble with monohydrated hydrogen phosphate ions into infinite single helices (TPA)2n[(HPO4·H2O)LS/R]n or (TBA)2n[(HPO4·H2O)LS/R]n. The predisposed point chirality next to the anion binding center in the ligands has a profound impact on the resulting assemblies, and their chirality is manipulated in a predictable manner.